Abstract
Ebola virus (EBOV) and Marburg virus (MARV) belong to the family Filoviridae and cause severe hemorrhagic fever in humans and nonhuman primates. Despite the discovery of EBOV (Reston virus) in nonhuman primates and domestic pigs in the Philippines and the serological evidence for its infection of humans and fruit bats, information on the reservoirs and potential amplifying hosts for filoviruses in Asia is lacking. In this study, serum samples collected from 353 healthy Bornean orangutans (Pongo pygmaeus) in Kalimantan Island, Indonesia, during the period from December 2005 to December 2006 were screened for filovirus-specific IgG antibodies using a highly sensitive enzyme-linked immunosorbent assay (ELISA) with recombinant viral surface glycoprotein (GP) antigens derived from multiple species of filoviruses (5 EBOV and 1 MARV species). Here we show that 18.4% (65/353) and 1.7% (6/353) of the samples were seropositive for EBOV and MARV, respectively, with little cross-reactivity among EBOV and MARV antigens. In these positive samples, IgG antibodies to viral internal proteins were also detected by immunoblotting. Interestingly, while the specificity for Reston virus, which has been recognized as an Asian filovirus, was the highest in only 1.4% (5/353) of the serum samples, the majority of EBOV-positive sera showed specificity to Zaire, Sudan, Cote d’Ivoire, or Bundibugyo viruses, all of which have been found so far only in Africa. These results suggest the existence of multiple species of filoviruses or unknown filovirus-related viruses in Indonesia, some of which are serologically similar to African EBOVs, and transmission of the viruses from yet unidentified reservoir hosts into the orangutan populations. Our findings point to the need for risk assessment and continued surveillance of filovirus infection of human and nonhuman primates, as well as wild and domestic animals, in Asia.
Highlights
Ebola virus (EBOV) and Marburg virus (MARV) are enveloped negative-strand RNA viruses belonging to the family Filoviridae
Orangutan serum samples were screened for IgG antibodies specific to each species of filoviruses (Figures S1 and S2), and all optical density (OD) values obtained by enzyme-linked immunosorbent assay (ELISA) were analyzed statistically
Endpoint antibody titers of positive samples ranged between 1:100 and 1:25600 (Table 1). Since these positive samples exhibited distinct specificity either to the EBOV or MARV GP antigen, it was confirmed that the high OD values given by these samples were not due to nonspecific antibody reaction to the bovine serum albumin used for blocking or impurities contained in GP antigen preparations
Summary
Ebola virus (EBOV) and Marburg virus (MARV) are enveloped negative-strand RNA viruses belonging to the family Filoviridae. Outbreaks of Ebola and Marburg hemorrhagic fever in humans and nonhuman primates (other than imported cases) have occurred sporadically in central and west Africa, but REBOV was first reported in 1989–1990 by several quarantine facilities in the United States, when wild-caught monkeys (Macaca fascicularis) imported from the Philippines became ill, with some dying [1]. No human case of filovirus hemorrhagic fever has been reported in Asian countries, the discovery of REBOV suggests the existence of REBOV in some wild animal species in Asia. It is suspected that filoviruses persist in some species of fruit bats that may serve as natural reservoirs [5,6,7]. Epidemiological studies suggest that index cases in outbreaks have often been linked to direct contact with apes presumably infected through bats or another reservoir species in Africa [8]. Filovirus infection has never been reported in any animal species, including humans and nonhuman primates, in Indonesia
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